Articulated caster

Abstract

A carriage including an articulated caster is disclosed. The carriage includes a frame with a load-supporting section and a base section that pivots relative to the load-supporting section and pivotally attaches to three casters. The frame further includes a pivot block that cooperates with the sections to provide a universal joint that permits the relative pivotal movement between the sections. The universal joint includes pivot axes that are spaced below the horizontal axes of the caster wheels so that forces applied by the load-supporting section through the joint are prevented from tipping the carriage. The caster wheels are spaced relative to the joint so that the base section provides a walking-beam suspension. The carriage further includes a preferred direction of travel whereby the casters are positioned on the base section to approach an obstacle in sequential order when traveling along the preferred direction.

1 . A caster-supported carriage for supporting a load above a surface, the carriage comprising: 
 a load-supporting frame section; and    a caster assembly including a base frame and at least three spaced apart caster wheels that are attached to and cooperatively support the base frame so that the caster assembly is self-supporting,    said load-supporting frame section and said caster assembly being pivotal relative to one another about a substantially horizontal base pivot axis,    each of said caster wheels including a wheel axis,    said base pivot axis being spaced closer to the surface than the wheel axes so as to reduce the risk of carriage tipping.    
   
   
       2 . The carriage as claimed in  claim 1 , 
 a pair of said caster wheels being spaced oppositely from the base pivot axis so that the caster assembly operates as a walking beam.    
   
   
       3 . The carriage as claimed in  claim 1 , 
 said load-supporting frame section and said caster assembly being pivotal relative to one another about at least two substantially orthogonal pivot axes, with one of the pivot axes being the base pivot axis.    
   
   
       4 . The carriage as claimed in  claim 3;  and 
 a pivot block pivotally attached to the base frame about a first one of the axes and being pivotal relative to the load-supporting frame section about a second one of the axes.    
   
   
       5 . The carriage as claimed in  claim 1 , 
 said load-supporting frame section and said caster assembly being pivotally interconnected at a pivotal joint permitting relative pivotal movement about the base pivot axis.    
   
   
       6 . The carriage as claimed in  claim 1;  and 
 an intermediate frame section pivotally interconnected to the base frame at a first pivotal joint permitting relative pivotal movement about the base pivot axis,    said intermediate frame section being pivotally interconnected to the load-supporting frame section at a second pivotal joint for permitting the load-supporting frame section to pivot relative to the intermediate frame section about an intermediate pivot axis,    said second pivotal joint being spaced laterally from the first pivotal joint so that the caster assembly is operable to translate vertically relative to the second pivotal joint about the intermediate pivot axis.    
   
   
       7 . The carriage as claimed in  claim 1;   an intermediate frame section pivotally interconnected to the base frame at a first pivotal joint permitting relative pivotal movement about the base pivot axis,    said intermediate frame section being pivotally interconnected to the load-supporting frame section at a second pivotal joint for permitting the load-supporting frame section to pivot relative to the intermediate frame section about an intermediate pivot axis,    a second caster assembly spaced from the first-mentioned caster assembly,    said second caster assembly including a second base frame and at least three spaced apart caster wheels that are attached to and cooperatively support the second base frame so that the second caster assembly is self-supporting,    said intermediate frame section being pivotally interconnected to the second base frame at a third pivotal joint.    
   
   
       8 . The carriage as claimed in  claim 7 , 
 said third pivotal joint permitting relative pivotal movement between the intermediate frame section and the second base frame about a second base pivot axis,    each of said caster wheels of the second caster assembly including a wheel axis,    said second base pivot axis being spaced closer to the surface than the wheel axes of the corresponding caster wheels so as to reduce the risk of carriage tipping.    
   
   
       9 . The carriage as claimed in  claim 7 , 
 said second pivotal joint being spaced between the first and third pivotal joints so that the intermediate frame section operates as a walking beam.    
   
   
       10 . The carriage as claimed in  claim 7 , 
 said third pivotal joint permitting relative pivotal movement between the intermediate frame section and the second base frame about a second base pivot axis,    said base pivot axes being substantially parallel to the intermediate pivot axis.    
   
   
       11 . The carriage as claimed in  claim 7 , 
 said first and third pivotal joints each permitting relative pivotal movement between the intermediate frame section and the respective base frame about at least two substantially orthogonal pivot axes.    
   
   
       12 . The carriage as claimed in  claim 11;  and 
 a pair of pivot blocks each interconnecting a corresponding one of the base frames and the intermediate frame section,    each of said pair of pivot blocks being pivotally attached to the intermediate frame section about a first one of the pivot axes and pivotally attached to the respective base frame about a second one of the pivot axes.    
   
   
       13 . The carriage as claimed in  claim 7 , 
 said base frames each including an opening that receives the intermediate frame section therein,    said base frames each being operable to contact the intermediate frame section along the respective opening in a selected orientation to limit relative pivotal movement therebetween.    
   
   
       14 . The carriage as claimed in  claim 7 , 
 said third pivotal joint permitting relative pivotal movement between the intermediate frame section and the second base frame about a second base pivot axis,    said intermediate frame section being pivotal relative to one of the base frames in a first direction about the respective base pivot axis,    said intermediate frame section being configured to engage said one of the base frames when said intermediate frame section has pivoted into a base-engaging position, wherein further pivoting of the intermediate frame section relative to said one of the base frames in the first direction is prevented,    one of said caster wheels of one of the corresponding caster assemblies being spaced from the corresponding pivotal joint in the first direction, such that any pivoting of the intermediate frame section in the first direction beyond the base-engaging position occurs about said one of said caster wheels.    
   
   
       15 . The carriage as claimed in  claim 14 , 
 said intermediate frame section contacting said one of the base frames at a contact location when said intermediate frame section is pivoted into the base-engaging position,    said one of said caster wheels being spaced further in the first direction from the corresponding pivotal joint than the contact location.    
   
   
       16 . The carriage as claimed in  claim 1 , 
 said caster wheels being spaced laterally from each other along a direction orthogonal to the base pivot axis so that the caster wheels are configured to approach a surface obstruction sequentially when the carriage moves along the orthogonal direction.    
   
   
       17 . A caster-supported carriage for supporting a load above a surface, the carriage comprising: 
 a load-supporting frame section; and    a caster assembly including a base frame and at least three spaced apart caster wheels that are attached to and cooperatively support the base frame section so that the caster assembly is self-supporting,    said load-supporting frame section and said caster assembly being pivotal relative to one another about a substantially lateral base pivot axis,    said caster wheels being spaced laterally from each other along a direction orthogonal to the base pivot axis so that the caster wheels are configured to approach a surface obstruction sequentially when the carriage moves along the orthogonal direction.    
   
   
       18 . The carriage as claimed in  claim 17 , 
 a pair of said caster wheels being spaced oppositely from the base pivot axis so that the caster assembly operates as a walking beam.    
   
   
       19 . The carriage as claimed in  claim 17 , 
 said load-supporting frame section and said caster assembly being pivotal relative to one another about at least two substantially orthogonal pivot axes, with one of the pivot axes being the base pivot axis.    
   
   
       20 . The carriage as claimed in  claim 19;  and 
 a pivot block pivotally attached to the base frame about a first one of the axes and being pivotal relative to the load-supporting frame section about a second one of the axes.    
   
   
       21 . The carriage as claimed in  claim 17 , 
 said load-supporting frame section and said caster assembly being pivotally interconnected at a pivotal joint permitting relative pivotal movement about the base pivot axis.    
   
   
       22 . The carriage as claimed in  claim 17;  and 
 an intermediate frame section pivotally interconnected to the base frame at a first pivotal joint permitting relative pivotal movement about the base pivot axis,    said intermediate frame section being pivotally interconnected to the load-supporting frame section at a second pivotal joint for permitting the load-supporting frame section to pivot relative to the intermediate frame section about an intermediate pivot axis,    said second pivotal joint being spaced laterally from the first pivotal joint so that the caster assembly is operable to translate vertically relative to the second pivotal joint about the intermediate pivot axis.    
   
   
       23 . The carriage as claimed in  claim 17;   an intermediate frame section pivotally interconnected to the base frame at a first pivotal joint permitting relative pivotal movement about the base pivot axis,    said intermediate frame section being pivotally interconnected to the load-supporting frame section at a second pivotal joint for permitting the load-supporting frame section to pivot relative to the intermediate frame section about an intermediate pivot axis; and    a second caster assembly spaced from the first-mentioned caster assembly,    said second caster assembly including a second base frame and at least three spaced apart caster wheels that are attached to and cooperatively support the second base frame so that the second caster assembly is self-supporting,    said intermediate frame section being pivotally interconnected to the second base frame at a third pivotal joint.    
   
   
       24 . The carriage as claimed in  claim 23 , 
 said third pivotal joint permitting relative pivotal movement between the intermediate frame section and the second base frame about a second base pivot axis,    said caster wheels of said second caster assembly being spaced laterally from each other along a direction orthogonal to the second base pivot axis so that said caster wheels of said second caster assembly are configured to approach a surface obstruction sequentially when the carriage moves along the orthogonal direction.    
   
   
       25 . The carriage as claimed in  claim 24 , 
 said caster wheels of said first and second caster assemblies being spaced laterally from each other along a direction substantially parallel to said orthogonal directions so that said caster wheels of said first and second caster assemblies are configured to approach a surface obstruction sequentially when the carriage moves along the direction.    
   
   
       26 . The carriage as claimed in  claim 23 , 
 said third pivotal joint permitting relative pivotal movement between the intermediate frame section and the second base frame about a second base pivot axis,    each of said caster wheels of the second caster assembly including a wheel axis,    said second base pivot axis being spaced closer to the surface than the wheel axes of the corresponding caster wheels so as to reduce the risk of carriage tipping.    
   
   
       27 . The carriage as claimed in  claim 23 , 
 said second pivotal joint being spaced between the first and third pivotal joints so that the intermediate frame section operates as a walking beam.    
   
   
       28 . The carriage as claimed in  claim 23 , 
 said third pivotal joint permitting relative pivotal movement between the intermediate frame section and the second base frame about a second base pivot axis,    said base pivot axes being substantially parallel to the intermediate pivot axis.    
   
   
       29 . The carriage as claimed in  claim 23 , 
 said first and third pivotal joints each permitting relative pivotal movement between the intermediate frame section and the respective base frame about at least two substantially orthogonal pivot axes.    
   
   
       30 . The carriage as claimed in  claim 29;  and 
 a pair of pivot blocks each interconnecting a corresponding one of the base frames and the intermediate frame section,    each of said pair of pivot blocks being pivotally attached to the intermediate frame section about a first one of the pivot axes and pivotally attached to the respective base frame about a second one of the pivot axes.    
   
   
       31 . The carriage as claimed in  claim 23 , 
 said base frames each including an opening that receives the intermediate frame section therein,    said base frames each being operable to contact the intermediate frame section along the respective opening in a selected orientation to limit relative pivotal movement therebetween.    
   
   
       32 . The carriage as claimed in  claim 23 , 
 said third pivotal joint permitting relative pivotal movement between the intermediate frame section and the second base frame about a second base pivot axis,    said intermediate frame section being pivotal relative to one of the base frames in a first direction about the respective base pivot axis,    said intermediate frame section being configured to engage said one of the base frames when said intermediate frame section has pivoted into a base-engaging position, wherein further pivoting of the intermediate frame section relative to said one of the base frames in the first direction is prevented,    one of said caster wheels of one of the corresponding caster assemblies being spaced from the corresponding pivotal joint in the first direction, such that any pivoting of the intermediate frame section in the first direction beyond the base-engaging position occurs about said one of said caster wheels.    
   
   
       33 . The carriage as claimed in  claim 32 , 
 said intermediate frame section contacting said one of the base frames at a contact location when said intermediate frame section is pivoted into the base-engaging position,    said one of said caster wheels being spaced further in the first direction from the corresponding pivotal joint than the contact location.